Engine-condition-responsive cutoff apparatus

ABSTRACT

Apparatus for inhibiting the operation of an engine in response to engine speeds which exceed a preset number of revolutions per minute employs a cutoff circuit for detecting and shaping firing signals and a switch interposed in either the ignition powering circuit, or the fuel circuit of a diesel, which is operable upon a detected predetermined overlap of a shaped signal and the previous signal delayed a predetermined interval. The apparatus also utilizes temperature and pressure-sensing devices which are effective to operate the cutoff circuit in response to the detection of adverse temperature or pressure conditions within the engine. An engine cutoff device, i.e. a relay, is operated in response to a true output from an OR gate which has as its inputs the overlap detection circuit and the individual sensing devices. The cutoff device and the OR gate are also provided as a separate package for applications which require engine conditions detection other than overspeed detection.

United States Patent [72] inventor LaDell Ray Swiden 1608 S. 1st, Sioux F818, 8. Dak. 57105 [21] AppL No. 868,973

[22] Filed Oct 13,1969

[45] Patented Aug. 24, 1971 Continuation-impart of application Ser. No. 780,441, Dec. 2, 1968, now abandoned.

[54] ENGINE-CONDI'I'lON-RESPONSIVE CUTOFF 3,356,082 12/1967 Jukes ABSTRACT: Apparatus for inhibiting the operation of an engine in response to engine speeds which exceed a preset number of revolutions per minute employs a cutoff circuit for detecting and shaping firing signals and a switch interposed in APPARATUS either the ignition powering circuit, or the fuel circuit of a 7 Claims, 13 Drawing Fm diesel, which is operable upon a detected predetermined overlap of a shaped signal and the previous signal delayed a [52] 1.1.8. CL 123/102, predetermined interval T apparatus also utilizes tempera. 123/ 198 D, 123/ 198 DB, 123/ 198 DC ture and pressure-sensing devices which are effective to Int. operate the cutgff circuit in response to the detection 0f ad. oiscarch ver e temperature or ressure onditions the engine 148 E, 140.3, 198 D, 198 DB, 198 DC; 317/5 An engine cutoff device, ie a relay, is operated in response to a true output from an OR gate which has as its inputs the over- [56] Reference Cned lap detection circuit and the individual sensing devices. The UNITED STATES PATENTS cutoff device and the OR gate are also provided as a separate 3,153,746 10/1964 Atkinson 317/5 package for applications which require engine conditions de- 3,182,648 5/1965 Schneider et a1. 123/148 E tection other than overspeed detection.

5 PUL 56 0544 Y 4 51 /1425? (7360 7 60 P A 5W/7C// M c/kcu/f PATENTED M24 1971 SHEET 1 []F 3 M NR 3 QR Q Q ENGINE-CONDI'I'ION-RESPONSIVE CU'I'OFF APPARATUS CROSSREFERENCES TO RELATED APPLICATION This application is a continuation-in-part of my prior application of the same title, Ser. No. 780,44l, filed Dec. 2, 1968, now abandoned.

BACKGROUND OF THE INVENTION l. Field of the invention This invention relates to apparatus for detecting adverse engine conditions and is particularly concerned with apparatus for inhibiting the operation of an engine in response to the detection of engine speeds which are in excess of a preset number of revolutions per minute, or the detection of abnormal temperature or pressure conditions.

2. Description of the Prior Art Heretofore, control of engine speed has been primarily limited to speed-governing-type apparatus wherein the engine, say an internal combustion engine, has the effects of loading of the engine compensated for by apparatus which adjusts fuel flow to the carburetor of the engine. Such governing techniques may be employed to control engine overspeed; however, engine overspeed in either a continuously loaded or unloaded condition indicates a recurring malfunction which should be repaired. Also, abnormal temperatures of coolant and lubricant and abnormal lubricant pressure are indications that should provide some type of an alarm to indicate that cor rective action should be taken. Speed-dependent clutches may also be employed to correct overspeed; however, these require a certain amount of maintenance attention and are not particularly adaptable to accurately provide engine cutoff speeds. An operator could detect any of the above conditions and manually shut down the engine; however, this would require .his constant attention, either visual or audible, to determine the occurrence of such a condition. Thus, it is highly desirable that apparatus be provided which automatically shuts down an engine in response to the detection of an adverse engine condition. Inasmuch as an automotive type engine may be operated as a prime mover in a variety of systems which are manned by operators of an undetermined background with respect to automotive equipment, apparatus for cutting ofi an engine should be easily installed and easily preset to a variety of predetermined numbers of required revolutions per minute, or pressure or temperature settings so that no special training would be necessary for an operator.

It is also highly desirable to provide apparatus for automatically curtailing the operation of an engine in response to the detection of an adverse condition externally of the engine. For example, it is desireable and advantageous to shut down an engine which is driving a generator in response to adverse conditions occurring within the generator, i.e. generator temperature conditions.

SUMMARY OF THE INVENTION According to the invention, apparatus is provided for opening the powering circuit of an ignition system or blocking the fuel circuit of a diesel system in response to an engine speed in excess of a preset number of revolutions per minute. The preferred embodiment of the invention is realized by the provision of circuit means for detecting the firing of the cylinders and providing electrical signals as indications of cylinder firing and means for converting the signals thus detected into pulse signals. The pulse signal and the previous signal delayed are fed into a circuit for comparing the duration of overlap between these two pulses. A switching circuit which comprises contacts included in the ignition-powering circuit (or a valve in a fuel line) is operated in response to pulse overlap in excess of a predetermined or preset interval which corresponds to the desired engine cutoff speed. Engine cutoff is positive in that, in a preferred embodiment of the invention, the switching circuit includes a controlled rectifier in a relay driving circuit. As is well known in the art, a controlled rectifier, once conductive, remains conductive with little sustaining input and can only be deactivated by opening its anode-cathode circuit. Ad vantageously, contacts of the ignition switch are employed for this purpose in the case of engines which have an ignition system.

According to the invention, apparatus is provided for opening the powering circuit of an ignition system or blocking the fuel circuit of a diesel system in response to the detection of adverse conditions, which conditions may be indication of engine operation or may be indirectly related to engine operation. A switching device is operated from any of a plurality of condition detection devices through the medium of an OR gate to inhibit engine operation by opening the engine-firing system. In the preferred embodiment, the switching device includes a relay and the OR gate includes a plurality of diodes. The relay is operatively connected to a solenoid valve in the case of diesel systems, and to the powering circuit in the case of ignition systems. Apparatus constructed in accordance with the principles of the present invention may be packaged as a complete enginecondition-responsive system, with or without the speed detection feature, as a hermetically sealed unit for mounting on or adjacent the engine.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention, its organization, construction and operation will be readily apparent from the following description of certain embodiments thereof which are illustrated in the drawings, although modifications thereof may be made without departing from the spirit and scope of the novel concepts thereof, and

FIG. 1 is a block diagram of engine overspeed cutoff apparatus according to the present invention;

FIG. 2 is a combination block diagram and symbolic representation of an embodiment of the invention;

FIG. 3 is a schematic circuit diagram showing the embodiment of FIG. 2 in greater detail;

FIG. 4 is a schematic diagram showing the temperature and pressure responsive apparatus which may be included in the circuit of FIG. 3;

FIG. 5 is a plan view of a packaged engine overspeed cutoff device according to the invention;

FIG. 6 is a partial block, partial schematic diagram of the circuit of FIG. 3 as it would appear modified to control a diesel system;

FIG. 7 is a schematic circuit diagram of a modification of the apparatus of FIG. 2 for sensing the output of a magnetic sender for diesel engine applications;

FIG. 8 is a schematic circuit diagram showing another modification of the apparatus of FIG. 2 having a magnetic pickup as source of engine speed information;

FIG. 9 is a graphical illustration of the input signal to the apparatus as modified in FIG. 8;

FIG. 10 is a schematic circuit diagram of apparatus according to the present invention for controlling engine cutoff in response to any one of several control conditions; and

FIGS. l1, l2 and 13 illustrate various circuit connections to *the apparatus of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates the invention as it pertains to an engine having an ignition system as comprising a pulse shaper l, as the input circuit which detects ignition spark signals and transforms these signals into shaped pulse signals. The apparatus further includes a delay circuit connected to the pulse shaper 1 and having its output connected to a comparator 3. A second input to comparator 3 is extended directly from the output of the pulse shaper 1, so that the inputs to the comparator 3 are a shaped pulse and the previous pulse. delayed. Connected to the output of the comparator 3 is a switch 4 which has a portion thereof interposed in the ignition-powering circuit and which is operable upon detection of a preset amount of pulse overlap to open the ignition-powering circuit.

The above is brought out more clearly in FIG. 2 which shows an embodiment of the invention wherein the pulse shaper 1 comprises an input-shaping circuit which has its output connected to a monostable multivibrator 20. The input shaping circuit 10 detects the spark signals from the ignition system and forms a trigger therefrom for the monostable multivibrator 20. Monostable multivibrator upon receipt of the trigger operates in a well known fashion to provide an output pulse having a pulse width which is determined by the timing portion (e.g. capacitor 26, FIG. 3) of the monostable circuit.

The delay circuit above-referred to includes in this instance a NOR gate or inverter circuit which operates on the trailing edge of the output pulse of the monostable multivibrator 20 to provide a triggering signal for monostable multivibrator 40. Multivibrator operates in a manner similar to that of monostable circuit 20 to provide an output pulse which is essentially the same as the output pulse of monostable multivibrator 20, except it is delayed a predetermined interval due to the reformation of the signal through circuits 30 and 40. The shaped pulse and the previous pulse delayed are applied to an AND gate 50, as a means of determining overlap between the two signals. The signal overlap at the output of an AND circuit is employed as a pulse input to a unijunction transistor circuit 60. The unijunction transistor circuit has an input which detects the duration of the overlap signal and which fires its unijunction transistor in response to an overlap signal in excess of a predetermined duration. The unijunction transistor circuit 60, is, in turn, employed to operate a controlled rectifier circuit (65, FIG. 3) which has a relay 66 connected in series therewith and which is also interposed in the powering circuit of the ignition system. Therefore, upon receipt of an overlap signal at the input to the unijunction circuit 60, the relay is operated to open the powering circuit of the ignition system.

The above embodiment is shown in greater detail and in connection to the ignition system of an automotive engine in FIG. 3. In the circuit shown, the input circuit 10 comprises a resistor 11, a capacitor 12, a resistor 13, and an output resistor 14. The input to circuit 10 is connected to an adequate source of spark signal, preferably at the points or the ignition coil of the ignition system. The spark signal is developed as an input to monostable multivibrator 20 over resistances ll, 13 and 14, capacitor 12 being effective as a high frequency ground to the complex spark signal. The monostable multivibrator 20 includes a transistor 21 having its collector connected to a ource of positive potential through resistor 22 and its emitter conne ted to ground through resistor 25. The circuit also includ. second transistor 23 which has it collector connected to a positive potential through resistor 24 and its emitter connected to ground through resi: tor 25. The base of transistor 23 is also connected to the positive potential through resistor 27 and a timing capacitor 26 is connected between the base of transistor 23 and the collector transistor 21. It can easily be seen from the drawing that, with the bias potentials thus applied, transistor 23 is the normally conducting transistor and transistor 21 if the normally nonconducting transistor of the monostable multivibrator 20.

An inverter circuit 30, (or single input NOR gate) receives its input through resistor 31 from the output 29 of the monostable multivibrator 20. The inverter circuit 30 includes a transistor 32 having its base connected to resistor 31, its collector connected to a source of positive potential through resistor 33 and its emitter connected to ground. The collector of transistor 32 is also coupled to the anode of diode 36 through a capacitor 34. The anode of diode 36 is also connected to ground through a resistor 35. A positive-going input signal to this circuit, due to the turning off of transistor 23, causes transistor 32 to conduct for the duration of the output pulse of monostable multivibrator 20 and the negative-going trailing edge of such output turns off transistor 32. This causes the output pulse of transistor 32 to be an inversion of the output of the monostable multivibrator 20. This inverted pulse is coupled by capacitors 34 to the anode of diode 36 where the positive-going trailing edge thereof causes conduction of diode 36 and provides a trigger for monostable multivibrator 40.

The monostable multivibrator 40 is essentially the same as monostable multivibrator 20. This circuit comprises transistor 41 having its base connected to the cathode of diode 36 for receiving the input triggering signal, its collector connected to a positive potential through resistor 42 and its emitter connected to ground through resistor 45. Further, a transistor 43 has its collector connected to positive potential through resistor 44 and its emitter connected to ground by way of resistor 45. The monostable multivibrator 40 also includes a timing capacitor 46 connected between the base transistor 43 and the collector of transistor 41 and a resistor 48 connected between the base of transistor 41 and the collector of transistor 43. The primary difference between the monostable multivibrator 40 and the monostable multivibrator 20 resides in the resistance connected between the base of transistor 43 and the positive potential. In monostable multivibrator 20 this was a single resistor 27: in monostable multivibrator 40 it is a resistance which includes a fixed resistor 47a and a variable resistor 47b. This variable portion of the circuit is effective to adjust the apparatus for different engine operating speeds. In operation, the engine speed would be increased to the desired cutoff speed and the variable resistance 47b would be adjusted until the cutoff is attained. The variance of resistance 47b operates to vary the quasistable state of the monostable multivibrator 40 and thus provide a variation of output pulse width. A single fixed resistance would provide a fixed predetermined shutdown point.

The output 29 of monostable multivibrator 20 and the output 49 of monostable multivibrator 40 are connected to diodes 51 and 52 respectively, of AND gate 50. A resistor 53 is connected between the anodes of diodes 51, 52 and the source of positive potential. Also connected to the anodes of diodes 51, 52 is a capacitor 54 which serves to develop an input signal for firing the unijunction transistor of circuit 60. The unijunction circuit 60 comprises a unijunction transistor 61 having a first base connected to ground through resistor 62 and a second base connected to the source of positive potential through resistor 63 and a firing electrode connected in common with the anodes of diodes 51, 52, resistor 53 and capacitor 54. Upon an overlap of a delay pulse from the monostable multivibrator 40 and the next shaped pulse from monostable multivibrator 20, the diodes S1, 52 are reversed biased and permit the capacitor 54 to be charged over resistor 53 from the source of positive potential. When the charging of capacitor 54 reaches a firing level for unijunction circuit 60, unijunction transistor 61 fires and current flows from the source of positive potential through the resistor 63, unijunction transistor 61, and resistor 62 to ground. A resistor 64 which is connected to the first base of the unijunction transistor couples the potential developed by the voltage divider so formed to the gate electrode of a controlled rectifier 65. The diode 65 conducts to establish a current flow from a second source of positive potential through relay winding 66 and the diode 65 to ground. Relay winding 66 has a set of normally closed contacts 67 operatively coupled thereto and electrically connected between the battery of the ignition system and the spark-generating apparatus of the ignition system. Therefore, the power for the sparkgenerating apparatus is disconnected from such apparatus and the engine is cutoff.

Inasmuch as a controlled rectifier will sustain its conductive condition after the removal of a triggering input to its gate, some means must be provided for resetting this circuit to its nonconductive condition. Advantageously, the engine is inoperative at this point and must be restarted; therefore, a set of contacts of the ignition switch are interposed between the battery input terminal B and the direct current supply 70 of the overspeed cutoff apparatus. The circuit 70 comprises a first output VI for connection to the relay winding 66, a resistor 71, a breakdown diode 72 and a capacitor 73 for providing a second and lower stable source of potential V for the components of the remainder of the cutoff apparatus.

FIG. 4 illustrates the switch portion of FIG. 3 as it may appear modified to operate in response to adverse temperature or pressure conditions. An OR gate 90 is formed by a plurality of diodes 91-93 connected through relay winding 66, each of these diodes having an input which is connectable to ground via a respective condition sensing device 94-96. These devices sense internal engine conditions on an analog basis. For example, sensor 94 is associated with the temperature of the engine system coolant; sensor 95 is associated with the temperature of the engine lubricant; and sensor 96 is concerned with the pressure of the lubricant. The sensors continuously detect conditions of the engine and each may provide'an enabling ground potential to its corresponding diode upon detection of an adverse condition to complete an operating circuit for relay winding 66. The sensors may be of a variable setting type or may be of a quick-change type for easy conversion of permissable temperature or pressure conditions. Generally though, fixed components will suffice for a number of different engines having substantially the same normal pressure and temperature conditions.

FIG. 5 illustrates an engine overspeed cutoff device as it may appear as a sealed package. This unit comprises a cover 100 having a pair of mounting flanges 101 with mounting holes 102 therein. A terminal strip 103 provides for the necessary connection between the ignition system and the working components interior of the cover 100. As indicated in the drawing for a negative ground ignition system, terminal A+ is for connection to the ignition switch (or it may be connected to COIL if no ballast is used); terminal GND is to be connected to the frame; terminal PTS is for connection to the points (may also be connected to the ignition coil); terminal COIL PWR is for connection to the ignition switch; and terminal COIL is for connection to the positive terminal of the ignition coil.

in a particular design for a l2-volt negative ground system, an overspeed device provided the following tabulated speed control ranges.

ENGINE R.P.M. RANGE 4 Cycle, 8 Cylinder l,300-7,000

4 Cycle, 6 Cylinder l,500-l0,000

4 Cycle, 4 Cylinder 210044.000

FIG. 6 illustrates the application of the circuit of FIG. 3 to a diesel engine wherein a pickup transducer 107, either photoelectric or magnetic, feeds the ignition representative signals to an input shaper 10a for processing as hereinbefore described. A predetermined amount of overlap turns on the controlled rectifier 65 and provides an operating path for solenoid winding 104 for shutting off its associated valve 105 in a fuel line between the fuel tank 106 and the remainder of the fuel system. A switch 80a corresponds to the ignition switch 80 of FIG. 3 for restoring the controlled rectifier 65 to its nonconductive condition.

FIG. 7 illustrates the apparatus of FIG. 3 having a modified input circuit 110 to receive an input signal indicative of engine speed from a magnetic pickup at input terminal 111. The circuit of FIG. 7 is referenced to that of FIG. 3 by the point a and the monostable circuit 20. The input circuit 110 therefore replaces the input shaper 10 (elements ll, 12 and 13) of FIG. 3 and comprises a clipping amplifier and differentiator circuit. A representative input signal to terminal 111 would be a 50- volt peak to peak sine wave of a frequency that is proportional to engine speed. One proportion employed for the frequency was three time engine speed. The input signal is fed to the speed-determining circuit in response to the positive portions of the cycle by way of transistor 117, the triggering signal for the monostable circuit 20 being developed across resistor diode 114 provides negative clipping. A diode 121 provides a definite trigger level for the monostable circuit 20 to initiate speed determination as set forth above in the discussion of FIG. 3.

FIG. 8 illustrates another modification of the speed sensing input circuit which is designed to operate in response to a more generalized magnetic sender, generally referenced 131. This circuit is referenced to FIG. 3 by point b and the monostable circuit 20. FIG. 9 illustrates input signals c and d which are generated by the magnetic sender 131 and fed via capacitor 132 to the base of transistor 136 which is biased normally conductive. The negative peaks of signals 0 and d pulse off the transistor 136 and the voltage rise at the collector thereof is employed to operate the monostable circuit 20.

FIG. 10 illustrates a condition-responsive cutoff unit 140 hermetically sealed in a housing 141 (illustrated in phantom) and comprising a plurality of circuit terminals 142-150. Terminals 143, 145 and 146 form signal input terminals for receiving ground signals from pressure, temperature, etc. senders, as illustrated in FIGS. 4 and 12. A plurality of diodes 151-153 have their anodes connected in common and their cathodes connected to respective ones of terminals 143, 145 and 146 to form an OR gate. The anodes of the diodes 151-153 are also connected to a relay winding and an arc suppression diode which elements are in turn connected to a terminal 147 which carries the A+ potential.

An external warning lamp 159 may be connected across relay winding 155 by connecting such a lamp to terminals 142 and 144 as illustrated in FIG. 11.

The circuit illustrated in FIG. 10 is universal for both ignition and diesel systems as shown in FIG. 13. With A+ applied at terminal 148 operation of relay winding 155 and transfer of contact 156 may be employed, for example, to complete an operating circuit to a normally open solenoid fuel flow valve 162 via contact 158 and terminal 150. By the same token contacts 156 and 157 may open an ignition system, or contacts 156 and 158 may complete an operating path for a slave relay to open an ignition circuit. Also the relay may be employed to operate auxiliary devices, such as clutches, gears, etc., as well as ignition circuits and fuel valves.

One unit constructed in accordance with FIG. 10 employed four IN9I4 diodes for elements ISL-154 and a Price Electric relay, No. 28 El 1 1 AE to great advantage.

I claim: 1

1. Apparatus for cutting off ignition power to an engine having a spark-generating ignition system in response to adverse engine-operating conditions, comprising:

an ignition-powering circuit including a source of power connected to the ignition system;

means connected to the ignition system for detecting successively occurring spark signals;

means for delaying said signals;

means connected to said detecting means and said delaying means for timing the overlap between a signal and the delayed previous signal; means connected to said engine for detecting temperature conditions of said engine; and means connected to said timing means and to said temperature-detecting means and interposed in said powering circuit between said source of power and the ignitionsystem for opening said powering circuit in response to a predetermined overlap of a signal and the delayed previous signal and in response to detection of engine temperature in excess of a predetermined temperature, said means for opening said ignition-powering circuit including switch means in said powering circuit, and an OR gate having a first input connection to said timing means, a second input connected to said means for detecting temperature conditions, and an output connected to said switch means for operating same upon detection of predetermined pulse overlap or anexcessive temperature condition.

2. Apparatus for cutting off ignition power to an engine having a spark-generating ignition system in response to adverse engine-operating conditions, comprising:

an ignition-powering circuit including a source of power connected to the ignition system;

means connected to said ignition system for detecting successively occurring spark signals;

means for timing the overlap between a signal and the delayed previous signal;

means connected to said engine for detecting pressure con- .ditions within said engine; and

means connected to said timing means and to said pressuredetecting means and interposed in said powering circuit between said source of power and the ignition system for opening said powering circuit in response to the detection of a predetermined overlap of a signal and the delayed previous signal and in response to the detection of a pressure within said engine below a predetermined pressure, said means for opening said powering circuit including switch means connected in said powering circuit and operable to open said powering circuit, and an OR gate having a first input connected to said timing means, a second input connected to said pressure-detecting means, and an output connected to said switch means for operating said switch means upon detection of a predetermined pulse overlap or an insufficient pressure condition.

occurring fuel firings and generating corresponding firing signals indicative of speed;

means for delaying said signals; timing means connected to said delaying means for timing the overlap between a signal and the delayed previous signal to detect excess engine speed;

means connected to said engine for detecting at least one adverse-engine-operating condition other than excess speed; and cut off means connected to both said timing means and said adverse-condition-detecting means and interposed in the fuel firing system for rendering the engine inoperative, said cutoff means including switch means in the fuel-firing system and operable to render the fuel-firing system inoperative, and an OR gate including a first input connected to said timing means, a second input connected to said adverse-condition-detecting means and an output connected to said switch means for operating said switch means in response to the detection of excess pulse overlap or an adverse engine-operating condition.

4. Apparatus according to claim 3, wherein said delay means comprises a monostable multivibrator for effecting said delay, said fuel firing-detecting means includes means operable to generate bipolar signals, and a clipping amplifier and a differentiator circuit for converting said bipolar signals into pulse signals for said multivibrator.

5. Apparatus according to claim 4, wherein said monostable multivibrator includes an adjustable circuit for determining signal width of the delayed signal.

6. Apparatus according to claim 3, wherein said timing means includes an AND circuit for detecting pulse overlap and means for detecting the duration of pulse overlap.

7. Apparatus according to claim 6, wherein said means for detecting pulse overlap comprises a unijunction transistor circuit including an input electrode and an output electrode, said means for detecting the duration of pulse overlap connected between said input electrode and said AND circuit for firing said unijunction transistor circuit, and said switch means includes a solid-state switching device and a solenoid cutoff device connected in the fuel-firing system and operated by said solid-state switching device, said solid-state switching device including a gate electrode connected to said unijunction transistor circuit whereby firing of said unijunction transistor circuit effects operation of said solid-state switching device.

Patent No. 6n1 1(13 Dated august 25 1 921 Inventor(s,) LaDell Ray Swiden It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines 35 and 36, "to accurately provide engine cutoff speeds." should read to accurately provide engine cutoff at a variety of desired cutoff speeds. Column 3, line 62, "if" should read is Signed and sealed this 1st day of August 1972.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents h u clwrumunu v-nrurm'. nrrur van-I 4:: 1n 

1. Apparatus for cutting off ignition power to an engine having a spark-generating ignition system in response to adverse engineoperating conditions, comprising: an ignition-powering circuit including a source of power connected to the ignition system; means connected to the ignition system for detecting successively occurring spark signals; means for delaying said signals; means connected to said detecting means and said delaying means for timing the overlap between a signal and the delayed previous signal; means connected to said engine for detecting temperature conditions of said engine; and means connected to said timing means and to said temperaturedetecting means and interposed in said powering circuit between said source of power and the ignition system for opening said powering circuit in response to a predetermined overlap of a signal and the delayed previous signal and in response to detection of engine temperature in excess of a predetermined temperature, said means for opening said ignition-powering circuit including switch means in said powering circuit, and an OR gate having a first input connection to said timing means, a second input connected to said means for detecting temperature conditions, and an output connected to said switch means for operating same upon detection of predetermined pulse overlap or an excessive temperature condition.
 2. Apparatus for cutting off ignition power to an engine having a spark-generating ignition system in response to adverse engine-operating conditions, comprising: an ignition-powering circuit including a source of power connected to the ignition system; means connected to said ignition system for detecting successively occurring spark signals; means for delaying said signals; means connected to said detecting means and said delaying means for timing the overlap between a signal and the delayed previous signal; means connected to said engine for detecting pressure conditions within said engine; and means connected to said timing means and to said pressure-detecting means and interposed in said powering circuit between said source of power and the ignition system for opening said powering circuit in response to the detection of a predetermined overlap of a signal and the delayed previous signal and in response to the detection of a pressure within said engine below a predetermined pressure, said means for opening said powering circuit including switch means connected in said powering circuit and operable to open said powering circuit, and an OR gate having a first input connected to said timing means, a second input connected to said pressure-detecting means, and an output connected to said switch means for operating said switch means upon detection of a predetermined pulse overlap or an insufficient pressure condition.
 3. Apparatus for cutting off an engine in response to adverse-operating conditions of an engine which includes a fuel-firing system which produces successively occurring fuel firings, comprising: means connected to said engine for detecting successively occurring fuEl firings and generating corresponding firing signals indicative of speed; means for delaying said signals; timing means connected to said delaying means for timing the overlap between a signal and the delayed previous signal to detect excess engine speed; means connected to said engine for detecting at least one adverse-engine-operating condition other than excess speed; and cut off means connected to both said timing means and said adverse-condition-detecting means and interposed in the fuel firing system for rendering the engine inoperative, said cutoff means including switch means in the fuel-firing system and operable to render the fuel-firing system inoperative, and an OR gate including a first input connected to said timing means, a second input connected to said adverse-condition-detecting means and an output connected to said switch means for operating said switch means in response to the detection of excess pulse overlap or an adverse engine-operating condition.
 4. Apparatus according to claim 3, wherein said delay means comprises a monostable multivibrator for effecting said delay, said fuel firing-detecting means includes means operable to generate bipolar signals, and a clipping amplifier and a differentiator circuit for converting said bipolar signals into pulse signals for said multivibrator.
 5. Apparatus according to claim 4, wherein said monostable multivibrator includes an adjustable circuit for determining signal width of the delayed signal.
 6. Apparatus according to claim 3, wherein said timing means includes an AND circuit for detecting pulse overlap and means for detecting the duration of pulse overlap.
 7. Apparatus according to claim 6, wherein said means for detecting pulse overlap comprises a unijunction transistor circuit including an input electrode and an output electrode, said means for detecting the duration of pulse overlap connected between said input electrode and said AND circuit for firing said unijunction transistor circuit, and said switch means includes a solid-state switching device and a solenoid cutoff device connected in the fuel-firing system and operated by said solid-state switching device, said solid-state switching device including a gate electrode connected to said unijunction transistor circuit whereby firing of said unijunction transistor circuit effects operation of said solid-state switching device. 